Motion-picture film



' that Charges m7 Patented Oct. 23, 1923.

UNITED STATES P Axralvr OFFICE.

MOTION-PICTURE FILM.

Application led August 13, 1919. Serial No. 317,163.

To all whom t may concern.'

Be it known that I, CLARENCE J. CoBERLY, a citizen of the United States,residing at Los Angeles, Ainthe county of Los Angeles and State ofCalifornia, have invented a new and useful .Improvement Comprising aMotion-Picture Film, ofl which the follow ing isa specification.

My invention relates to motion picture films and an o'bject of theinvention is to provide means for preventing the film from being markedby disruptive discharges of static electricity.. Static electricity isat the present time a sourre of considerable loss in the motion pictureindustry, due to the fact of this electricity are collected on the fidischarging over the surface thereof, and thereby producing a markingwhich ruins the film for projection purposes. These markings may beformed during the process of manufacture, but it is probable that thegreat majority of such markings are produced in the'camera due tofriction or induction or both. It is often necessary to retake scenesdue to the fact that the film is found marred by static markings afterit has been developed, thus Causing considerable losses.

These static markings are undoubtedly due to the fact that the Celluloidof which the films are ordinarily made is a fairly good insulator sothat Considerable otentials may be built up thereon with tie result thatwhen they discharge they produce these objectionable markings. If itwere possible to provide a transparent material which was a goodconductor of electricity and to substitute this material for theCelluloid, ordinarily used, these static markings could be prevented,for the reason thattlie charges would be Conducted away from the film asfast as they were formed without the disruptive discharges which producethe actinic rays which cause the markings on the film. I am not aware ofany substance which would be suitable for the manufacture of film whichis a good. Conductor, but I have found that the ordinary celluloid film,or support can be coated with material which is a good Conductor andthat when so coated troublesV` with static entirely disappear. .Onemethod of accomplishing this is to deposit on the surface of thecelluloid a fine layer of highly hygroscopic material, this materialcollecting "moisture from the air and maintaining a fine layer ofmoisture on the surface which any electrical wCharges are electrolyticall lconducted to the conducting members o the camera. I havedisclosed a method by which this may be accomplished in my applicationSerial No. 147,505, filed February 8, 1917. The present applicationcomprisesl an improvement in the invention setforth in the earlierapplication.

I have found while it is veryeasy and quite practical to providea'coating which may be applied by any one to any film, that it is erhapsbetter tojincorporate a conducting ayer in the film itself at the timeof manufacture and I disclose such a film and a `method of producing itherein. In the annexed drawing which is entirely diagrammatic and forillustrative purposes only,

Fig. 1 is a perspective view of the film with the various layers turnedback.

Fig. 2 is a section on a very muchlenlarged scale showing a film withthe layer sandwiched 'between two layers of Celluloid.

F ig. 3 is a similar view showing the Conducting layer laced between thesensitized emulsion and t e Celluloid support.

Fig. 4 is a section on a very much enlarged scale7 through still anotherform of my invention.

The film shown in Figs. 1 and 2 consist of two layers 11 and 12 oftransparent slipporting material such as Celluloid between of the filmthrough which can conveniently be formed of a thin layer of gelatine orother colloidal binder which contains a hygroscopic salt, or anelectrolyte, lithium chloride being a Convenient substance to use inthis connection. The sensitized emulsion 14 is placed on one side of theCelluloid.

The gelatine solution may consist of the following materials: Distilledwater, 450 cubic centimeters, grain alcohol, 550 cubic centimeters, hardgelatine, 10 grams, lithium chloride, 2 to 2% grams.

The gelatine layer 13 may be very thin, the lithium chloride thereintending to lkeep it moist by absorbing moisture from the air. Thecharges formed on the surface of the film leak through the CelluloidCoating to the conducting layer 13 through which these electricalCharges are electrolytically conducted away without disruptivedischarges.

.I have also found that the type of film shown in Fig. 3 will alsoprevent static.

This 'izn consisting of a Celluloid support 30 and conducting layer 31upon which the sensitized emulsion 32 is placed. This film eithersurface readily leak or are conducted through the celluloid to theconducting layer beneath as fast as these Vcharges are formed andwithout disruptive discharges., This is of course due to the large areaand extremely short length of the conducting path the area being equaltothe areaof the Vso film on which the charge accumulates and the lengthbeing the thickness of the film.

While I have shown a single conducting layer sandwiched betweenmoderately. thick supporting layers, it it possible to produce a verysatisfactory film by building up alternate layers of gelatine andCelluloid each of these layers being very thin so that the conductingmaterialvis very uniformly and com letel distributed throughout the bodyof t e fi y is illustrated in Figure 4, in which the emulsion is carriedon a support formed of Celluloid layers 5l, between which aredistributed conducting material 52. This gen` eral distribution of theconducting material through the film can sired degree, the number ofconducting layers being made of any desired number.

I claim as my invention 1. .A motion picture film comprising: asupporting strip; a layer of sensitized emulsion; and a transparentlayer of high electrical conductivity between said strip and saidemulsion. i

2. A motion picture film comprising: a supporting strip; a. layer ofsensitized emulsion; and a sufficiently high electrical conductivity toprevent the static markings which would be formed in said emulsion underordinary con- 1n. This method of construction be carried to anydetransparent conducting layer of ditions of use were such conductinglayer not present, said conducting layer being between said emulsion andsaid supporting strip.

4. A motion picture filmhaving a layer containing an electrolytecarried' in a suitablebinder,.said electrolyte being sufiicientlyelectrically conducting to prevent, under the ordinary conditions of useof said film, the static markings which Would be produced by such usewere said electrolyte not present. 5. A motion picture film comprising:a layer of sensitized emulsion; two supporting strips of transparentmaterial; and a transparent layer of high electrical conductivitybetween said strips.

6. A motion picture film comprising 5 a y layer of sensitized emulsion;a supporting strip of transparent material, said layer and strip beingso constituted, if used alone, that staticmarking would be produced insaid eiulsion under ordinary conditions of use; and material ofsufiiciently high electrical conductivity to prevent said markings,isaidmaterial being incorporated in and carried by said strip.

7. A motion -picture film comprising: a

layer of sensitized emulsion; a supporting strip or transparentmaterial, said layer and strip being so constituted, if used alone, thatstatic marking would be produced in said emulsion `under ordinaryconditions of use; and hygroscopic material of sufficiently highelectrlcal conductivity to prevent said markings, said material beingincorporated in and carried by said strip.

In testimony whereof, I have hereunto set my hand at i 8th day of August1919.

CLARENCE J. COBERLY.

Los Angeles, California, this

